Locking unit with end-position locking catch for a seatbelt retractor

ABSTRACT

The invention relates to a locking unit ( 4 ) for a seat belt retractor ( 1 ), which locking unit ( 4 ) is provided at one end of a seat belt spool ( 3 ) of the seat belt retractor ( 1 ), on which a seat belt ( 2 ) is retracted, so that when the seat belt ( 2 ) is quickly unrolled a locking arm ( 14 ) of a locking lever ( 13 ) is locked with an internal gearwheel (Z), as a result of which the seat belt spool ( 3 ) is locked, wherein the locking unit ( 4 ) has the following elements:
     the locking lever ( 13 ) with a centre of rotation (D) arranged spaced apart from the centre of the seat belt spool ( 3 ), an actuator arm ( 15 ) and the locking arm ( 14 );   a triggering unit having an inertia weight ( 17 ), a counter-pressure spring ( 18 ) and a transmission arm, which engages with the actuator arm ( 15 ), wherein the triggering unit is formed to rotate the locking lever ( 13 ) about the centre of rotation (D) and to lock the locking arm ( 14 ) by means of the stationary internal gearwheel (Z) that is arranged about the locking lever ( 13 ) in the case of a fast acceleration of the unrolling of the safety belt ( 2 ), conditioned by the inertia force of the inertia weight ( 17 ) acting against the spring force of the counter-pressure spring ( 18 ), wherein a cover ring ( 19 ) is provided between the locking lever ( 13 ) and the internal gearwheel (Z), which cover ring ( 19 ) can be rotated into a covering position when the seat belt ( 2 ) is retracted, in which covering position the cover ring ( 19 ) at least partially covers the region between the locking arm ( 14 ) and the internal gearwheel (Z) in order to prevent locking, and which can be rotated into a release position when the seat belt ( 2 ) is unrolled, in which release position the cover ring ( 19 ) releases the region between the locking arm ( 14 ) and the internal gearwheel (Z) in order to permit locking.

The invention relates to a locking unit for a seat belt retractor, whichlocking unit is provided at one end of a seat belt spool of the seatbelt retractor, on which a seat belt is retracted, so that when the seatbelt is quickly unrolled a locking arm of a locking lever is locked withan internal gearwheel, as a result of which the seat belt spool islocked, wherein the locking unit has the following elements:

the locking lever with a centre of rotation arranged spaced apart fromthe centre of the seat belt spool, an actuator arm and the locking arm;

a triggering unit having an inertia weight, a counter-pressure springand a transmission arm, which engages with the actuator arm, wherein thetriggering unit is formed to rotate the locking lever about the centreof rotation and to lock the locking arm with the stationary internalgearwheel that is arranged about the locking lever in the case of a fastacceleration of the unrolling of the safety belt, conditioned by theinertia force of the inertia weight acting against the spring force ofthe counter-pressure spring.

Such a locking unit is known from the document DE 10 2008 053 853 A1,wherein a seat belt system and the functions thereof are described ingreater detail. The known locking units is intended to discontinue theunrolling of the seat belt of a vehicle in the case of a collisionhaving happened and the belted up passenger being catapulted forwards.In this case, the unrolling velocity of the seat belt is more quicklyincreased than determined by the safety standards. A triggering unit ofthe known locking unit has an inertia weight and a coil spring as acounter-pressure spring. In the case of fast acceleration of the seatbelt spool, the inertia weight will retard the acceleration of thetriggering unit, which is why the inertia force of the inertia weightwill act against the spring force of the counter-pressure spring,Starting with a maximum acceleration of the unrolling process that isdetermined by the inertia weight and the spring force, there isinitiated that the locking lever is rotated against the spring forceabout the centre of rotation until the locking arm engages with theinternal gearwheel and locks the seat belt spool against furtherunrolling of the seat belt.

In the document mentioned above there is already made reference to theproblem of the end-position locking of the seat belt, which becomesapparent when the seat belt is retracted and the belt tongue abuts at avehicle component, for example. Upon the abrupt stopping of retractionthe inertia weight effectuates the triggering unit locking the seatbelt. if this locking is realized when the seat belt is more or lesscompletely retracted on the seat belt spool, then the locking cannot bereleased anymore by relaxing the seat belt, whereupon the seat beltretractor has to be unlocked by an authorized specialized workshop.

In order to prevent the end-position locking of the seat belt, the knownseat belt retractor has a locking unit with an end-position lockingcatch, which is formed by a planetary gearing having two gearwheels andtwo locking pegs, When the seat belt is retracted, the planetary gearingrotates the locking peg into a position, in which the locking arm of thelocking lever is blocked and rotating of the locking lever and thuslocking of the locking arm with the internal gearwheel is prevented.

In the known locking unit for a seat belt retractor it has shown to bedisadvantageous the construction of the end-position locking catch byway of the planetary gearing is complex and, hence, on the one side,prone to failures and, on the other side, also expensive to produce.

The invention is based on the task to provide an improved locking unitfor a seat belt retractor, which solves the problem of the end-positionlocking by way of a rather simple and reliable construction.

According to the invention, this task is solved by the provision of acover ring between the locking lever and the internal gearwheel, whichcover ring can be rotated into a covering position when the seat belt isretracted, in which covering position the cover ring at least partiallycovers the region between the locking arm and the internal gearwheel inorder to prevent locking, and which can be rotated into a releaseposition when the seat belt is unrolled, in which release position thecover ring releases the region between the locking arm and the internalgearwheel in order to permit locking.

Thereby, there is achieved the advantage that by means of a simple coverring, dependent on the direction of rotation of the seat belt spool ofthe seat belt retractor, the locking arm may engage with the internalgearwheel for locking or be prevented to do so by the cover ring.

Further advantageous embodiments of the invention will be described ingreater detail in the following by way of the figures.

FIG. 1 shows a seat belt retractor having a locking in an exploded view.

FIG. 2 shows the internal gearwheel, the cover ring and the lockinglever of the locking unit according to FIG. 1.

FIG. 3 shows the triggering unit of the locking unit according to FIG.1.

FIG. 4 shows the assembled seat belt retractor according to FIG. 1 whenthe seat belt is being retracted.

FIG. 5 shows the assembled seat belt retractor according to FIG. 1 whenthe seat belt is being unrolled.

FIG. 1 shows a seat belt retractor 1 of the seat belt system of avehicle in an exploded drawing. It is the task of the seat beltretractor 1 to retract the seat belt 2 on a seat belt spool 3 and tostop unrolling of the seat belt 2 in the case of a vehicle collision.For this reason, the seat belt retractor 1 has a locking unit 4, theindividual parts and function thereof will be explained in greaterdetail in the following.

The seat belt retractor 1 further has a housing having two housing parts5 and 6 as well as a mainspring 7 including spring housing 7 forretracting the seat belt 2. In the seat belt spool 3 there is provided aseat belt shaft 9, through which there is inserted an insert 10, whereinthe seat belt shaft 9 as well as the insert 10 is positivelyaccommodated in the seat belt spool 3 and rotated together with the seatbelt spool 3.

The locking unit 14 that is partly illustrated in greater detail in theFIGS. 2 and 3 is positively mounted at one end of the seat belt spool 3on the insert 10. The locking unit 4 has an annular gear 11 with aninternal gearwheel Z, wherein the annular nu II is connected with thehousing and, consequently, does not rotated when the seat belt 2 isretracted and unrolled. In the seat belt shaft 9 there is provided arecess spaced apart from the centre of the seat belt spool 3 or the axisof rotation thereof, respectively, in which a centre of rotation D of alocking lever 13 is rotatably arranged. The locking lever 13 may berotated about the centre of rotation D into a locking position and intoa release position. In the locking position the locking unit 4, via theinsert 10 and the seat belt shaft 9, blocks the rotation of the seatbelt spool 3, whereas the seat belt spool 3 may be freely rotated in therelease position.

The locking lever 13 further has a locking arm 14, at the end of whichthree locking teeth VZ are provided. If the locking lever 13 has beenmoved into its locking position, then the three locking teeth VZ willengage with three teeth gaps of the internal gearwheel Z, thus blockingthe seat belt spool 3. The locking lever 3 further has an actuator arm15, with which a transmission arm of the triggering unit depicted inFIG. 3 will engage.

The triggering unit is formed by a gearwheel 16, an inertia weight 17and a cod spring 18, as a sensitivity spring of the triggeringmechanism, as well as a catch 12. The transmission arm that is engagedwith the locking arm 15 of the locking lever 13 is provided at thebottom side of the gearwheel 16 illustrated in FIG. 3. The gearwheel 16is situated on the catch 12, which in turn is situated on the insert 10and rotates together with the seat belt spool 3 via the seat belt shaft9. The gearwheel 16 is rotatably mounted in the catch 12, wherein therange of rotation is restricted to a determined angular range, whichcorresponds exactly to the adjustment path of the locking lever 13between the locking position and the release position thereof. The coilspring 18 is clamped between the catch 12 and the gearwheel 16, rotatingthe gearwheel 16 and—via the transmission arm of the gearwheel 16—alsothe locking lever 13 in a rest position into the release position of thelocking lever 13. The inertia weight 17 is firmly clamped in thegearwheel 16.

If the rotational velocity of the seat belt spool 3, for example in thecase of a vehicle collision, is rapidly increased because a passenger ispushed into the seat belt 2, then the catch 12 quickly accelerates withthe seat belt spool 3. Due to the weight of the inertia weight 17 aninertia force acts against this acceleration, whereupon the gearwheel 16then falls behind in regard to the catch 12 in opposition to the. springforce of the coil spring 18 and adjusts the locking lever 13. Thedimensions of the inertia weight 17 and the coil spring 18 determinethat acceleration of the seat belt spool 3, at which the locking lever13 is adjusted into the locking position thereof by the triggering unit,thus preventing the further rotation of the seat belt spool 3.

The locking unit 4 of the seat belt retractor 1 further has anend-position locking catch, which is formed by a cover ring 19 and arecess A in a part of the perimeter of the seat belt shaft 9. The coverring 19 has a catch lug N, which sits closely at the first end stop A1of the recess A of the seat belt shaft 9 when the seat belt 2 isunrolled from the seat belt roll 3 and at the second end stop A2 of therecess A of the seat belt shaft 9 when the seat belt 2 is retracted ontothe seat belt roll 3. The cover ring 19 further has a diameter D and aheight H, wherein the cover ring 19 only has the height H1 in a segmentsection of a circle K. An edge R of the cover ring 19 is thusdiscontinued across the segment section of the circle K.

The cover ring 19 now further has three spring elements F, which sitedgingly at the housing in the assembled state, which is why the coverring 19 is slowed down through friction in regard to the rotating seatbelt shaft 9 but still rotated along between the two end stops A1 andA2. The cover ring 19 is rotated in the assembled state by the rotatingseat belt shaft 9 so that the discontinuation of the edge R will stop atthe position of the locking lever 13 when unrolling so that the lockingteeth VZ of the locking arm 14 may engage with the internal gearwheel Zand lock the seat belt roll 3. When the seat belt 2 is retracted on theseat belt roll 3, the cover ring 19 is then rotated by the seat beltshaft 9 so that the edge R will stop at least between one of the lockingteeth VZ and the internal gearwheel Z and so that, as a consequence,locking will be prevented when retracting is suddenly stopped.

In FIG. 4, the seat belt retractor 1, which is completely assembled butfor the housing, is illustrated with the seat belt 2 being retractedonto the seat belt roll 3. The annular gear 11 is depicted onlypartially in order to better visualize the cover ring 19 situatedunderneath. The recess A at the perimeter of the seat belt shaft 9 hasan angular range W from the first end stop A1 to the second end stop A2.During retraction, the catch lug N of the cover ring 19 sits at thesecond end stop A2, as the cover ring 19 has been rotated clock-wiseaccording to the recess A in the seat belt shaft 9. In this position ofthe cover ring 19 the circular sector K of the cover ring 19 is situatedin the covering position, in which the cover ring 19 at least partiallycovers the region between the three locking teeth VZ and the internalgearwheel Z. Indeed, only two of the three locking teeth VZ are visiblein FIG. 4, as the third locking tooth VZ is situated behind the edge Rof the cover ring 19, which is why the locking lever 13 cannot lock,even in the case of very abrupt stopping of the retraction of the seatbelt 2. In this way, end-position locking is thus prevented when theseat belt 2 is retracted.

In FIG. 5 the seat belt retractor 1 according to FIG. 4 is illustrated,wherein in this case a passenger has unrolled the seat belt 2 veryabruptly from the seat belt spool 3, such as in the case of a vehiclecollision, which is why the locking unit 4 has locked further unrolling.The locking teeth VZ are locked in place in the tooth gaps of theinternal gearwheel Z. This locking position of the locking lever 13 wasmade possible by the cover ring 19 having been rotated with the catchlug N thereof at the first end stop A1 of the seat belt shaft 9 when theseat belt 2 was unrolled in order to adjust the cover ring 19 into therelease position thereof.

The cover ring 19 thus does not prevent normal locking of the seat beltretractor 2 when the seat belt 2 is unrolled, which is why there hasbeen created by the cover ring 19 a safe and reliable construction inorder to prevent end-position locking when the seat belt 2 is retracted.

By determining the segment section of the circle K with an angular rangeof 10 to 40 degree and in particular of about 25 degree sufficientstability of the cover ring 19 will be guaranteed. By making provisionof the locking lever 13 and the internal gearwheel Z being made of metalthere is achieved the advantage that these components are especiallystable and durable when locking. By making provision of two or severallocking teeth there is achieved the advantage that the high forces,which are developed in a vehicle collision when the unrolling the seatbelt 2 is locked, may be better drained off.

There is to be noted that the locking lever may also have other forms inorder to fulfil the functionality described. The triggering unit mayalso be configured in a different way, as the part in the end-positionlocking catch that is essential for the invention is formed by the coverring. It would also be possible for the cover ring to have no catch lugbut rather a catch slot, with which a catch lug of the catch engages.

There is to be noted that the cover ring may be made of metal as well asa plastic material. It has been proven to be especially advantageous toform the cover ring from glass fibre reinforced plastic material, suchas, for example, PA 6.6 having 30% glass fibres, POM having 30% glassfibres. Using such a plastic material will enable the realization of thespring elements and helps to decrease production costs.

1. A locking unit for a seat belt retractor, which locking unit isprovided at one end of a seat belt spool of the seat belt retractor, onwhich a safety belt is retracted, so that when the seat belt is quicklyunrolled a locking arm of a locking lever is locked with an internalgearwheel, as a result of which the seat belt spool is locked, whereinthe locking unit has the following elements: the locking level with acentre of rotation arranged spaced apart from the centre of the seatbelt spool, an actuator arm and the locking arm; a triggering unithaving an inertia weight, a counter-pressure spring and a transmissionarm, which engages with the actuator arm, wherein the triggering unit isformed to rotate the locking lever about the centre of rotation and tolock the locking arm with the stationary internal gearwheel that isarranged about the locking lever in the case of a fast acceleration ofthe unrolling of the safety belt, conditioned by the inertia force ofthe inertia weight acting against the spring force of thecounter-pressure spring, characterized in that a cover ring is providedbetween the locking lever and the internal gearwheel, which cover ringcan be rotated into a covering position when the seat belt is retracted,in which covering position the cover ring at least partially covers theregion between the locking arm and the internal gearwheel in order toprevent locking, and which can be rotated into a release position whenthe seat belt is unrolled, in which release position the cover ringreleases the region between the locking arm and the internal gearwheelin order to permit locking.
 2. The locking unit according to claim 1,wherein a seat belt shaft is provided in the seat belt spool securedagainst rotation, at the end of which facing the locking unit there isprovided a recess at the perimeter, which has a first end stop and asecond end stop, and that the cover ring has a catch lug, which engageswith the recess of the seat belt shaft, wherein the catch lug sitsclosely at the first end stop when the seat belt is unrolled and at thesecond end stop when the seat belt is retracted.
 3. The locking unitaccording to claim 1, wherein the cover ring has a diameter and a firstheight, wherein the cover ring has only a second height in a segmentsection of a circle in order to release the locking arm in this segmentsection of a circle in order to lock with the internal gearwheel.
 4. Thelocking unit according to claim 1, wherein the segment section of thecircle has an angular range of 10 to 40 degrees and in particular about25 degrees of the perimeter of the cover ring.
 5. The locking unitaccording to claim 1, wherein the locking lever and the internalgearwheel are made of metal.
 6. The locking unit according to claim 1,wherein the locking arm has two and in particular three locking teeth,which are in each case configured to engage with a tooth gap of theinternal gearwheel.
 7. The locking unit according to claim 1, whereinthe counter-pressure spring is formed by a coil spring.
 8. The lockingunit according to claim 1, wherein the cover ring has at least onespring element, and in particular three spring elements, which sitedgingly at the housing in order to rotate the cover ring depending onthe direction of rotation of the seat belt shaft (9) by means of itscatch lug between the first end stop and the second end stop.
 9. Thelocking unit according to claim 1, wherein the cover ring is made fromplastic material, in particular from glass fibre reinforced plasticmaterial.
 10. A seat belt retractor of a seat belt system for retractingand unrolling a seat belt for a passenger, characterized in that theseat belt retractor has a locking unit according to claim 1.